Report on Suwanosejima (Japan) — March 1989

Scientific Event Alert Network Bulletin, vol. 14, no. 3 (March 1989)
Managing Editor: Lindsay McClelland.

Suwanosejima (Japan) Explosions and ashfall; 1988 activity summarized

Please cite this report as:

Global Volcanism Program, 1989. Report on Suwanosejima (Japan). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 14:3. Smithsonian Institution.

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29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)

On 1, 14, and 16 January, residents . . . heard explosions. Ash fell to the S on 21 and 24 January in the the only inhabited part of the small island. On 7 February at 1225, an explosion sound was heard, and on 28 February, a 1,000-m-high ash plume deposited large amounts of ash to the S. At 1640 on 3 March, the crew of a JAS aircraft observed a 2,000-m ash cloud. A summary of [1987-88] explosions and ashfall is shown in table 2.

Table 2. Eruptive episodes at Suwanose-jima, January 1987-October 1988. Courtesy of JMA.

[Skip text table]
    1988       Plume     Activity
             Height (m)

    Jan 05       --      Four explosions
        16      300      Five explosions
        17      500      Four explosions
        18      300      One explosions
    Feb 29       --      Explosion at 1325 caused air shock
    Mar 08      500      Eleven explosions accompanied by air shock
        28       --      Three explosions accompanied by air shock
    Apr 13      500      Five or six explosions per minute
        14      500      40-50 explosions
        15     2000      TOA Domestic Airlines pilot saw the plume
                           rising 2000 m
        16      500      Ashfall in the S part of the island
    Jul 18     3000      Southwest Airlines pilot saw the ash plume rising
    Aug 09     2000      Japan Air System pilot saw the plume rising 2000 m
        13      500      Ashfall in the S part of the island
        29      300      Several explosions, ashfall
    Oct 03      500      Ashfall in the S part of the island
        06       --      Rumbling, ashfall in the S
        07       --      Rumbling, ashfall in the S

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: JMA.